Part 6: Ending the Epidemic

African Prostitutes May Play a Crucial Role in Developing an HIV Vaccine

NAIROBI, KENYAIn this city's Pumwani slum, everything seems inverted. Pumwani is one of the Kenyan capital's red-light districts, but the action happens during the day. After dark, it gets too dangerous even for prostitutes. Then there's the way the women advertise: no hip-high skirts or brazen busts. Instead, says Joshua Kimani, a charismatic young doctor who runs a research clinic for sex workers, a prostitute is "whoever sits outside their doorway looking clean."

But the most profound turnabout centers on women like Joyce, who lives in a room hardly big enough for her bed. Joyce, who asked that her real name not be used, came to Nairobi from Tanzania. With three children to feed, she turned to prostitution within a year. That was 1983.

illustration: Katherine Streeter; photo: Mark Schoofs

After testing negative for 11 years, Selina got infected. Was stopping prostitution a risk factor?

No one knows exactly when HIV entered Nairobi. But in 1985, Canadian researcher Frank Plummer was studying gonorrhea and chlamydia among Pumwani sex workers, and almost as an afterthought he decided to add an HIV test. Two-thirds of the women tested positive. He shifted his focus to HIV.

Joyce was one of the lucky uninfected womenin fact, her luck was nothing short of astonishing. Fourteen years have passed since her original HIV test, and she has spent half those years servicing up to 10 johns a day. Yet she has remained HIV-negative even as the percentage of infected prostitutes topped 90 percent. She contracted other STDs, proving that her partners didn't use condoms and that she was almost certainly being exposed to HIV. But Joyce didn't get it.

Joyce was certainly unusual, but not unique. Indeed, Plummer made a curious discovery: If a sex worker didn't contract the virus after five years, she was unlikely ever to get it. The simplest explanation was that women like Joyce were resistant to HIValmost uninfectableand that's why these sex workers electrified the scientific community. They were, in the understated language of researchers, "multiply exposed but uninfected."

Prostitutes have been the scapegoats for AIDS in Africa, where the disease is spread mainly by heterosexual sex, and where men blame sex workers for bringing down AIDS. But, in the richest of ironies, Joyce and other prostitutes have provided researchers with valuable clues to the intricate workings of the immune system, and especially how it might be able to fend off the virus. In fact, the knowledge researchers gained from these women has been translated into a promising vaccine that is about to be tested in humans. The scapegoats of Africa's epidemic just might turn out to rank among its saviors.

Only a vaccine can end the AIDS epidemic.

The powerful new AIDS drugs, besides being too expensive for developing countries, do not cure the disease. In America and Europe, drug resistance and severe side effects are undermining the treatment of more and more patients, and the notion that HIV could be purged from the body has been shattered. The virus, which integrates into a patient's own DNA, appears to persist for life.

In theory, behavioral changes could stop the epidemic, and many Africans look to Uganda for hope. Ugandan president Yoweri Museveni aggressively confronted the epidemic, and infection rates in some urban areas have declined dramatically since the early 1990s; one surveillance site found that the prevalence of the virus has fallen by half. Yet even at that site, more than 13 percent of pregnant women are still infecteda huge pool of HIV-positive people. While education certainly can save millions, the fact is that behavioral change has never managed to halt the epidemic, not even in wealthy countries.

But vaccination has eradicated one diseasesmallpoxand is on the verge of eliminating a secondpolio. Ugandan researcher Roy Mugerwa, principal investigator of Africa's first AIDS vaccine trial, says, "We have learned from history that the only way to halt epidemics is with a vaccine."

Vaccines do not fight off infection; instead, they teach the immune system to recognize and attack the microbe. The world's first vaccine, for smallpox, was the cowpox virus, which causes only mild symptoms in people but primes the immune system for smallpox. Salk's polio vaccine was simply a killed polio virus. Technology has advanced, but the principle remains the same as when the ancient Chinese used to blow pulverized smallpox scabs through a bone into people's noses: Train the immune system with a dummy virus.

But can the body be taught to fight off HIV? There was a time when many scientists came close to despair, and many still harbor doubts. After all, AIDS attacks the immune system itself, and it kills almost everyone it infects. There were always people who recovered from smallpox, and there were many more who never even showed symptoms because they fought off the virus so quickly. But the more scientists learned about the natural history of AIDS, the more it seemed that everyone infected would succumb and that no one could repel the virus.

This is why the Pumwani prostitutes are so important. It's also why "people didn't believe us in the beginning," recalls Omu Anzala, one of the researchers who studied the Pumwani women. Had the sex workers really come in contact with the virus? They certainly didn't test antibody-positive, the classic trace of an infection. So maybe, despite all their johns, they had never encountered the virus.